The present invention relates to surge arrestors and, more particularly, to T-body elbow arrestors.
As described in U.S. Pat. No. 5,128,824, conventional surge arresters used to protect underground and overhead high voltage electrical systems widely employ metal oxide varistor elements to provide either a high or a low impedance current path between the arrester terminals depending on the voltage appearing across the varistor elements themselves. More particularly, at the system's steady state or normal operating voltage, the varistor elements have a relatively high impedance. As the applied voltage is increased, as in response to a lightening strike, their impedance decreases until the voltage appearing across the elements reaches their breakdown voltage, at which point their impedance rapidly decreases towards zero and the varistor elements become highly conductive. In this highly conductive condition, the varistor elements serve to conduct the resulting transient follow-on current to ground. As the transient overvoltage due to the strike and the follow-on current dissipate, the varistor elements' impedance increases effectively removing the short to ground and restoring the varistor elements and electrical system to their normal steady state condition.
Conventional elbow arresters are designed for 200 A load break application and have a 200 A standard interface (bushing) that is not compatible with the 600 A standard interface (bushing). The interfaces may differ not only in shape but in the method of coupling to the bushing. Such an arrangement is illustrated in FIG. 1, where a 600 A bushing extender accommodates a 600/200 A loadbreak reducing tap plug (LRTP), which in turn interfaces to a 200 A elbow arrestor. Thus, for users who need to apply surge protection to 600 A systems, a 200 A load break elbow arrester 50 is used in conjunction with a 600 A/200 A LRTP 40 and a 600 A bushing extender 10. An end 42 of the LRTP 40 is configured to receive a conventional 200 A elbow arrester 50. Furthermore, a coupling member 30 couples the LRTP 40 to a 600 A bushing 20, which is mounted on an apparatus bulkhead 8, in the bushing extender 10. A conventional 200 A detent arrangement 40′ is shown for coupling the LRTP 40 to the elbow arrestor 50.